The incident is said to have taken place at around 1am Monday following a confrontation.
The man is said to have tracked down the woman who was living with a friend after they separated a while ago.
The woman was stabbed in the neck.
It is not clear what triggered the altercation but police suspect the couple had relationship issues prior to the attack.
Nyeri Central Sub-County Police Commander Paul Kuria told the Nation that a manhunt has been launched for the suspect who has since gone into hiding.
“He took off as soon as he committed the act. We are currently looking for him,” Mr Kuria said.
Still in Nyeri, a 30-year-old woman is nursing serious injuries in Mathira after being stabbed 17 times, reportedly by her husband, over the weekend.
The suspect later surrendered himself to the police and has been placed in custody.
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